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The source code is released under:
Apache License
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/* * Copyright 2007 ZXing authors//w ww .ja v a 2 s. co m * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.justyoyo.contrast.common; import java.util.Arrays; /** * <p>A simple, fast array of bits, represented compactly by an array of ints internally.</p> * * @author Sean Owen */ public final class BitArray implements Cloneable { private int[] bits; private int size; public BitArray() { this.size = 0; this.bits = new int[1]; } public BitArray(int size) { this.size = size; this.bits = makeArray(size); } // For testing only BitArray(int[] bits, int size) { this.bits = bits; this.size = size; } public int getSize() { return size; } public int getSizeInBytes() { return (size + 7) / 8; } private void ensureCapacity(int size) { if (size > bits.length * 32) { int[] newBits = makeArray(size); System.arraycopy(bits, 0, newBits, 0, bits.length); this.bits = newBits; } } /** * @param i bit to get * @return true iff bit i is set */ public boolean get(int i) { return (bits[i / 32] & (1 << (i & 0x1F))) != 0; } /** * Sets bit i. * * @param i bit to set */ public void set(int i) { bits[i / 32] |= 1 << (i & 0x1F); } /** * Flips bit i. * * @param i bit to set */ public void flip(int i) { bits[i / 32] ^= 1 << (i & 0x1F); } /** * @param from first bit to check * @return index of first bit that is set, starting from the given index, or size if none are set * at or beyond this given index * @see #getNextUnset(int) */ public int getNextSet(int from) { if (from >= size) { return size; } int bitsOffset = from / 32; int currentBits = bits[bitsOffset]; // mask off lesser bits first currentBits &= ~((1 << (from & 0x1F)) - 1); while (currentBits == 0) { if (++bitsOffset == bits.length) { return size; } currentBits = bits[bitsOffset]; } int result = (bitsOffset * 32) + Integer.numberOfTrailingZeros(currentBits); return result > size ? size : result; } /** * @see #getNextSet(int) */ public int getNextUnset(int from) { if (from >= size) { return size; } int bitsOffset = from / 32; int currentBits = ~bits[bitsOffset]; // mask off lesser bits first currentBits &= ~((1 << (from & 0x1F)) - 1); while (currentBits == 0) { if (++bitsOffset == bits.length) { return size; } currentBits = ~bits[bitsOffset]; } int result = (bitsOffset * 32) + Integer.numberOfTrailingZeros(currentBits); return result > size ? size : result; } /** * Sets a block of 32 bits, starting at bit i. * * @param i first bit to set * @param newBits the new value of the next 32 bits. Note again that the least-significant bit * corresponds to bit i, the next-least-significant to i+1, and so on. */ public void setBulk(int i, int newBits) { bits[i / 32] = newBits; } /** * Sets a range of bits. * * @param start start of range, inclusive. * @param end end of range, exclusive */ public void setRange(int start, int end) { if (end < start) { throw new IllegalArgumentException(); } if (end == start) { return; } end--; // will be easier to treat this as the last actually set bit -- inclusive int firstInt = start / 32; int lastInt = end / 32; for (int i = firstInt; i <= lastInt; i++) { int firstBit = i > firstInt ? 0 : start & 0x1F; int lastBit = i < lastInt ? 31 : end & 0x1F; int mask; if (firstBit == 0 && lastBit == 31) { mask = -1; } else { mask = 0; for (int j = firstBit; j <= lastBit; j++) { mask |= 1 << j; } } bits[i] |= mask; } } /** * Clears all bits (sets to false). */ public void clear() { int max = bits.length; for (int i = 0; i < max; i++) { bits[i] = 0; } } /** * Efficient method to check if a range of bits is set, or not set. * * @param start start of range, inclusive. * @param end end of range, exclusive * @param value if true, checks that bits in range are set, otherwise checks that they are not set * @return true iff all bits are set or not set in range, according to value argument * @throws IllegalArgumentException if end is less than or equal to start */ public boolean isRange(int start, int end, boolean value) { if (end < start) { throw new IllegalArgumentException(); } if (end == start) { return true; // empty range matches } end--; // will be easier to treat this as the last actually set bit -- inclusive int firstInt = start / 32; int lastInt = end / 32; for (int i = firstInt; i <= lastInt; i++) { int firstBit = i > firstInt ? 0 : start & 0x1F; int lastBit = i < lastInt ? 31 : end & 0x1F; int mask; if (firstBit == 0 && lastBit == 31) { mask = -1; } else { mask = 0; for (int j = firstBit; j <= lastBit; j++) { mask |= 1 << j; } } // Return false if we're looking for 1s and the masked bits[i] isn't all 1s (that is, // equals the mask, or we're looking for 0s and the masked portion is not all 0s if ((bits[i] & mask) != (value ? mask : 0)) { return false; } } return true; } public void appendBit(boolean bit) { ensureCapacity(size + 1); if (bit) { bits[size / 32] |= 1 << (size & 0x1F); } size++; } /** * Appends the least-significant bits, from value, in order from most-significant to * least-significant. For example, appending 6 bits from 0x000001E will append the bits * 0, 1, 1, 1, 1, 0 in that order. */ public void appendBits(int value, int numBits) { if (numBits < 0 || numBits > 32) { throw new IllegalArgumentException("Num bits must be between 0 and 32"); } ensureCapacity(size + numBits); for (int numBitsLeft = numBits; numBitsLeft > 0; numBitsLeft--) { appendBit(((value >> (numBitsLeft - 1)) & 0x01) == 1); } } public void appendBitArray(BitArray other) { int otherSize = other.size; ensureCapacity(size + otherSize); for (int i = 0; i < otherSize; i++) { appendBit(other.get(i)); } } public void xor(BitArray other) { if (bits.length != other.bits.length) { throw new IllegalArgumentException("Sizes don't match"); } for (int i = 0; i < bits.length; i++) { // The last byte could be incomplete (i.e. not have 8 bits in // it) but there is no problem since 0 XOR 0 == 0. bits[i] ^= other.bits[i]; } } /** * * @param bitOffset first bit to start writing * @param array array to write into. Bytes are written most-significant byte first. This is the opposite * of the internal representation, which is exposed by {@link #getBitArray()} * @param offset position in array to start writing * @param numBytes how many bytes to write */ public void toBytes(int bitOffset, byte[] array, int offset, int numBytes) { for (int i = 0; i < numBytes; i++) { int theByte = 0; for (int j = 0; j < 8; j++) { if (get(bitOffset)) { theByte |= 1 << (7 - j); } bitOffset++; } array[offset + i] = (byte) theByte; } } /** * @return underlying array of ints. The first element holds the first 32 bits, and the least * significant bit is bit 0. */ public int[] getBitArray() { return bits; } /** * Reverses all bits in the array. */ public void reverse() { int[] newBits = new int[bits.length]; // reverse all int's first int len = ((size-1) / 32); int oldBitsLen = len + 1; for (int i = 0; i < oldBitsLen; i++) { long x = (long) bits[i]; x = ((x >> 1) & 0x55555555L) | ((x & 0x55555555L) << 1); x = ((x >> 2) & 0x33333333L) | ((x & 0x33333333L) << 2); x = ((x >> 4) & 0x0f0f0f0fL) | ((x & 0x0f0f0f0fL) << 4); x = ((x >> 8) & 0x00ff00ffL) | ((x & 0x00ff00ffL) << 8); x = ((x >> 16) & 0x0000ffffL) | ((x & 0x0000ffffL) << 16); newBits[len - i] = (int) x; } // now correct the int's if the bit size isn't a multiple of 32 if (size != oldBitsLen * 32) { int leftOffset = oldBitsLen * 32 - size; int mask = 1; for (int i = 0; i < 31 - leftOffset; i++) { mask = (mask << 1) | 1; } int currentInt = (newBits[0] >> leftOffset) & mask; for (int i = 1; i < oldBitsLen; i++) { int nextInt = newBits[i]; currentInt |= nextInt << (32 - leftOffset); newBits[i - 1] = currentInt; currentInt = (nextInt >> leftOffset) & mask; } newBits[oldBitsLen - 1] = currentInt; } bits = newBits; } private static int[] makeArray(int size) { return new int[(size + 31) / 32]; } @Override public boolean equals(Object o) { if (!(o instanceof BitArray)) { return false; } BitArray other = (BitArray) o; return size == other.size && Arrays.equals(bits, other.bits); } @Override public int hashCode() { return 31 * size + Arrays.hashCode(bits); } @Override public String toString() { StringBuilder result = new StringBuilder(size); for (int i = 0; i < size; i++) { if ((i & 0x07) == 0) { result.append(' '); } result.append(get(i) ? 'X' : '.'); } return result.toString(); } @Override public BitArray clone() { return new BitArray(bits.clone(), size); } }